Tiled digital radiography detectors for long-length imaging

ABSTRACT

A digital radiographic detector having a radiolucent cover and housing at one or more edges of the detector allows radiographic imaging using multiple detector arrangements with overlapping edges that do not obstruct radiographic images captured thereby.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Application Ser. No.62/080,454, filed Nov. 17, 2014, in the name of Wojcik et al., andentitled TILED DIGITAL RADIOGRAPHY DETECTORS FOR LONG-LENGTH IMAGING.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to digital radiography (DR)imaging, in particular, to long-length imaging that requires multiple DRdetectors.

Special cassettes and films of extended length are sometimes used whenimaging a long segment of a subject, such as a human body, with ananalog screen-film technique. An x-ray source and the cassette are bothcentered to the subject to be examined and an x-ray collimator isadjusted to cover the imaging area, whereby a single x-ray exposure isperformed. Flat-panel DR detectors are usually limited to 43 cm inlength. For long-length imaging applications this would require separateexposures to be taken at different regions of the subject. In order tocreate a large, single composite image for diagnosis, the individuallycaptured images of the subject need to be stitched together usingdigital computer-implemented reconstruction techniques.

Two primary approaches are available to acquire long-length imagingexams with flat-panel detectors. In both methods, the detector movesfrom one imaging position to the next behind the subject. In one knownembodiment, the x-ray energy source moves (rotates or tilts) in order totrack and expose the detector. In this x-ray source tilting method, thecentral x-ray pointing direction varies from one exposure position tothe next to deliver the x-rays to the detector. In another knownembodiment, the x-ray source focal spot position is not stationary, buttranslates synchronously with the DR detector parallel to the detector'saxis of travel.

There are advantages to both embodiments. For example, the tilt methodis free of parallax artifacts inherent in the x-ray source translationmethod. Because of parallax distortion, the geometric integrity of thesubject's features in the stitched image may be degraded, particularlyin the stitch overlap regions. Automatic image stitching can be achievedwith high geometric accuracy such as provided by the Carestream DRDirectView Long-Length Imaging System. A high-precision hardware encoderreports the exact detector travel distance between exposures. In adirection transverse to the detector motion axis, software automaticallyanalyzes the subject's features in the overlap regions to find the bestalignment between any two adjacent images. The total stitch error hasbeen demonstrated to be small under stringent exposure conditions.

Automatic exposure control can be used during the long-length imagingexams in order to apply just the right amount of exposure to each regionof the subject for image quality. Software may also automatically adjustexposure discrepancies and compensate for the latitude differences,therefore providing optimized image presentation for each image. Theimage-processing reconstruction algorithm stitches together theindividually optimized, display-presentation-ready images to create asmooth and seamless composite single image for diagnosis. The seam linebetween any two images may be blended without any visible artifactsduring this digital process. Such imaging software should be able toadjust and fine-tune stitch positions to compensate for movement of thesubject during the exam to avoid exposure retakes. In all of theexamples just described, it would be advantageous if multiple DRdetectors could be used to simultaneously capture a compositeradiographic image of a subject in a single exposure.

The discussion above is merely provided for general backgroundinformation and is not intended to be used as an aid in determining thescope of the claimed subject matter.

BRIEF DESCRIPTION OF THE INVENTION

A digital radiographic detector having a radiolucent cover and housingat one or more edges of the detector allows radiographic imaging usingmultiple detector arrangements with overlapping edges that do notobstruct radiographic images captured thereby. An advantage that may berealized in the practice of some disclosed embodiments of multiple DRdetector systems is that the images are simultaneously exposed andpotential movement of the subject during an imaging exam is eliminated,which results in improved long-length image reconstruction and reducedradiation exposure for a subject.

In one embodiment, a digital radiographic detector comprises amultilayer imaging structure with a substantially planar first sidehaving a surface area defined by a plurality of edges. A rigid,radio-opaque housing portion substantially encloses the multilayerstructure and surrounds one or more edges of the multilayer structure. Arigid, radiolucent housing portion is attached to the radio-opaquehousing portion and surrounds one or more of the edges of the multilayerstructure.

In another embodiment, a digital radiography detector comprises amultilayer structure. The multilayer structure includes a substantiallyplanar first side having a surface area defined by a plurality of edges.An imaging device layer is used to receive light energy. A scintillatorlayer is adjacent the device layer and is used to convert radiographicenergy to the light energy. A radiolucent layer covers the scintillatorlayer, and a rigid, radio-opaque housing substantially encloses themultilayer structure and surrounds one or more edges of the multilayerstructure. A rigid, radiolucent housing surrounds one or more edges ofthe multilayer structure.

In another embodiment, a long-length imaging system comprises three ormore digital radiographic detectors. A first detector comprises amultilayer structure with a substantially planar first side having asurface area defined by a plurality of edges. A device layer comprisinga plurality of photosensors absorb light energy and a scintillator layeradjacent the device layer converts radiographic energy to the lightenergy. A radiolucent layer covers the scintillator layer and a rigid,radio-opaque housing substantially encloses the multilayer structure andsurrounds one or more edges of the multilayer structure. A rigid,radiolucent housing surrounds one or more edges of the multilayerstructure. Second and third detectors are disposed behind the firstdetector, in relation to a radiographic energy source aimed at the atleast three detectors. Two of the edges of the first detectors overlapone edge of the second and third detectors.

In another embodiment, a long-length imaging system comprises three ormore digital radiographic detectors. First and second detectors eachcomprise a multilayer structure with a substantially planar first sidehaving a surface area defined by a plurality of edges. A device layerreceives light energy, and a scintillator layer adjacent the devicelayer converts radiographic energy to the light energy. A radiolucentlayer covers the scintillator layer, and a rigid, radio-opaque housingencloses the multilayer structure and surrounds one or more edges of themultilayer structure. A rigid, radiolucent housing portion surrounds oneor more of the edges of the multilayer structure, and a third detectorbehind the first and second detectors, is overlapped by each of thefirst and second detectors.

This brief description of the invention is intended only to provide abrief overview of subject matter disclosed herein according to one ormore illustrative embodiments, and does not serve as a guide tointerpreting the claims or to define or limit the scope of theinvention, which is defined only by the appended claims. This briefdescription is provided to introduce an illustrative selection ofconcepts in a simplified form that are further described below in thedetailed description. This brief description is not intended to identifykey features or essential features of the claimed subject matter, nor isit intended to be used as an aid in determining the scope of the claimedsubject matter. The claimed subject matter is not limited toimplementations that solve any or all disadvantages noted in thebackground.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features of the invention can beunderstood, a detailed description of the invention may be had byreference to certain embodiments, some of which are illustrated in theaccompanying drawings. It is to be noted, however, that the drawingsillustrate only certain embodiments of this invention and are thereforenot to be considered limiting of its scope, for the scope of theinvention encompasses other equally effective embodiments. For example,the summary descriptions above are not meant to describe individualseparate embodiments whose elements are not interchangeable. In fact,many of the elements described as related to a particular embodiment canbe used together with, and possibly interchanged with, elements of otherdescribed embodiments. Many changes and modifications may be made withinthe scope of the present invention without departing from the spiritthereof, and the invention includes all such modifications. The drawingsbelow are intended to be drawn neither to any precise scale with respectto relative size, angular relationship, relative position, or timingrelationship, nor to any combinational relationship with respect tointerchangeability, substitution, or representation of a requiredimplementation. In the drawings, like numerals are used to indicate likeparts throughout the various views. Thus, for further understanding ofthe invention, reference can be made to the following detaileddescription, read in connection with the drawings in which:

FIG. 1 is a diagram of an exemplary radiographic imaging system;

FIG. 2 is a schematic diagram of an imaging array for an exemplaryradiographic detector;

FIG. 3 shows a perspective view of an exemplary portable wireless DRdetector;

FIG. 4 is a cross-section of a portion of the exemplary portablewireless DR detector of FIG. 3 along section line A-A;

FIG. 5 is a diagram of an exemplary radiographic imaging systemillustrating positioning of the radiographic energy source and the DRdetector;

FIG. 6 is a cross-section of a portion of an exemplary portable wirelessDR detector according to one embodiment;

FIG. 7 is a cross-section of a portion of an exemplary portable wirelessDR detector according to one embodiment;

FIG. 8 is a cross-section of an exemplary arrangement of multiple DRdetectors in a radiographic imaging system according to one embodiment;

FIG. 9 is a cross-section of an exemplary arrangement of multiple DRdetectors in a radiographic imaging system according to one embodiment;

FIG. 10 is a top view of an exemplary arrangement of multiple DRdetectors in a radiographic imaging system according to the embodimentof FIG. 8;

FIG. 11 is a top view of an exemplary arrangement of multiple DRdetectors in a radiographic imaging system according to the embodimentof FIG. 9;

FIG. 12A is a perspective view of an imaging system implementing anarrangement of DR detectors according to one embodiment;

FIG. 12B is a perspective view of an imaging system implementing anarrangement of DR detectors according to one embodiment; and

FIG. 13 is a perspective view of an imaging system implementing anarrangement of DR detectors according to one embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view of a digital radiographic (DR) imagingsystem 10 that includes a generally planar DR detector 40 (shown withouta housing for clarity of description), an x-ray source 14 configured togenerate radiographic energy (x-ray radiation), and a digital monitor 26configured to display images captured by the DR detector 40, accordingto one embodiment. The DR detector 40 may include a two dimensionalarray 12 of detector cells 22 (photosensors), arranged in electronicallyaddressable rows and columns. The DR detector 40 may be positioned toreceive x-rays 16 passing through a subject 20 during a radiographicenergy exposure, or radiographic energy pulse, emitted by the x-raysource 14. As shown in FIG. 1, the radiographic imaging system 10 mayuse an x-ray source 14 that emits collimated x-rays 16, e.g. an x-raybeam, selectively aimed at and passing through a preselected region 18of the subject 20. The x-ray beam 16 may be attenuated by varyingdegrees along its plurality of rays according to the internal structureof the subject 20, which attenuated rays are detected by the array 12 ofphotosensitive detector cells 22. The planar DR detector 40 ispositioned, as much as possible, in a perpendicular relation to asubstantially central ray 17 of the plurality of rays 16 emitted by thex-ray source 14. The array 12 of individual photosensitive cells(pixels) 22 may be electronically addressed (scanned) by their positionaccording to column and row. As used herein, the terms “column” and“row” refer to the vertical and horizontal arrangement of the photosensor cells 22 and, for clarity of description, it will be assumed thatthe rows extend horizontally and the columns extend vertically. However,the orientation of the columns and rows is arbitrary and does not limitthe scope of any embodiments disclosed herein. Furthermore, the term“subject” may be illustrated as a human patient in the description ofFIG. 1, however, a subject of a DR imaging system, as the term is usedherein, may be a human, an animal, an inanimate object, or a portionthereof.

In one exemplary embodiment, the rows of photosensitive cells 22 may bescanned one or more at a time by electronic scanning circuit 28 so thatthe exposure data from the array 12 may be transmitted to electronicread-out circuit 30. Each photosensitive cell 22 may independently storea charge proportional to an intensity, or energy level, of theattenuated radiographic radiation, or x-rays, received and absorbed inthe cell. Thus, each photosensitive cell, when read-out, providesinformation defining a pixel of a radiographic image 24, e.g. abrightness level or an amount of energy absorbed by the pixel, that maybe digitally decoded by image processing electronics 34 and transmittedto be displayed by the digital monitor 26 for viewing by a user. Anelectronic bias circuit 32 is electrically connected to thetwo-dimensional detector array 12 to provide a bias voltage to each ofthe photosensitive cells 22.

Each of the bias circuit 32, the scanning circuit 28, and the read-outcircuit 30, may communicate with an acquisition control and imageprocessing unit 34 over a connected cable 33 (wired) or over a wirelesstransmitter 35. The DR detector may be equipped to transmit radiographicimage data, and to exchange control and other signals, such aspreparatory ready signals, over the cable 33 or wirelessly overtransmitter 35 with the acquisition control and image processing unit34, which may also include an image processing computer system. Theacquisition control and image processing unit 34 may include a processorand electronic memory (not shown) to control operations of the DRdetector 40 as described herein, including control of circuits 28, 30,and 32, for example, by use of programmed instructions. The acquisitioncontrol and image processing unit 34 may also be used to controlactivation of the x-ray source 14 during a radiographic exposure,controlling an x-ray tube electric current magnitude, and thus thefluence of x-rays in x-ray beam 16, and/or the x-ray tube voltage, andthus the energy level of the x-rays in x-ray beam 16.

The acquisition control and image processing unit 34 may transmit image(pixel) data to the monitor 26, based on the radiographic exposure datareceived from the array 12 of photosensitive cells 22. Alternatively,acquisition control and image processing unit 34 can process the imagedata and store it, or it may store raw unprocessed image data, in localor remotely accessible memory.

With regard to a direct detection embodiment of DR detector 40, thephotosensitive cells 22 may each include a sensing element sensitive tox-rays, i.e. it absorbs x-rays and generates an amount of chargecarriers in proportion to a magnitude of the absorbed x-ray energy. Aswitching element may be configured to be selectively activated to readout the charge level of a corresponding x-ray sensing element. Withregard to an indirect detection embodiment of DR detector 40,photosensitive cells 22 may each include a sensing element sensitive tolight rays in the visible spectrum, i.e. it absorbs light rays andgenerates an amount of charge carriers in proportion to a magnitude ofthe absorbed light energy, and a switching element that is selectivelyactivated to read the charge level of the corresponding sensing element.A scintillator, or wavelength converter, is disposed over the lightsensitive sensing elements to convert incident x-ray radiographic energyto visible light energy. Thus, in the embodiments disclosed herein, itshould be noted that the DR detector 40 (or DR detector 300 in FIG. 3 orDR detector 400 in FIG. 4) may include an indirect or direct type of DRdetector.

Examples of sensing elements used in sensing array 12 include varioustypes of photoelectric conversion devices (e.g., photosensors) such asphotodiodes (P-N or PIN diodes), photo-capacitors (MIS),photo-transistors or photoconductors. Examples of switching elementsused for signal read-out include MOS transistors, bipolar transistorsand other p-n junction components.

FIG. 2 is a schematic diagram 240 of a portion of a two-dimensionalarray 12 for a DR detector 40. The array of photosensor cells 212, whoseoperation may be consistent with the photosensor array 12 describedabove, may include a number of hydrogenated amorphous silicon (a-Si:H)n-i-p photodiodes 270 and thin film transistors (TFTs) 271 formed asfield effect transistors (FETs) each having gate (G), source (S), anddrain (D) terminals. In embodiments of DR detector 40 disclosed herein,such as a multilayer DR detector (400 of FIG. 4), the two-dimensionalarray of photosensor cells 12 may be formed in a device layer that abutsadjacent layers of the DR detector structure. A plurality of gate drivercircuits 228 may be electrically connected to a plurality of gate lines283 which control a voltage applied to the gates of TFTs 271, aplurality of readout circuits 230 may be electrically connected to datalines 284, and a plurality of bias lines 285 may be electricallyconnected to a bias line bus or a variable bias reference voltage line232 which controls a voltage applied to the photodiodes 270. Chargeamplifiers 286 may be electrically connected to the data lines 284 toreceive signals therefrom. Outputs from the charge amplifiers 286 may beelectrically connected to a multiplexer 287, such as an analogmultiplexer, then to an analog-to-digital converter (ADC) 288, or theymay be directly connected to the ADC, to stream out the digitalradiographic image data at desired rates. In one embodiment, theschematic diagram of FIG. 2 may represent a portion of a DR detector 40such as an a-Si:H based indirect flat panel imager as described belowwith respect to the exemplary embodiments of FIGS. 4, 6, and 7.

Incident x-rays, or x-ray photons, 16 are converted to optical photons,or light rays, by a scintillator, which light rays are subsequentlyconverted to electron-hole pairs, or charges, upon impacting the a-Si:Hn-i-p photodiodes 270. In one embodiment, an exemplary detector cell222, which may be equivalently referred to herein as a pixel, mayinclude a photodiode 270 having its anode electrically connected to abias line 285 and its cathode electrically connected to the drain (D) ofTFT 271. The bias reference voltage line 232 can control a bias voltageof the photodiodes 270 at each of the detector cells 222. The chargecapacity of each of the photodiodes 270 is a function of its biasvoltage and its capacitance. In general, a reverse bias voltage, e.g. anegative voltage, may be applied to the bias lines 285 to create anelectric field (and hence a depletion region) across the pn junction ofeach of the photodiodes 270 to enhance its collection efficiency for thecharges generated by incident light rays. The image signal representedby the array of photosensor cells 212 may be integrated by thephotodiodes while their associated TFTs 271 are held in a non-conducting(off) state, for example, by maintaining the gate lines 283 at anegative voltage via the gate driver circuits 228. The photosensor cellarray 212 may be read out by sequentially switching rows of the TFTs 271to a conducting (on) state by means of the gate driver circuits 228.When a row of the pixels 22 is switched to a conducting state, forexample by applying a positive voltage to the corresponding gate line283, collected charge from the photodiode in those pixels may betransferred along data lines 284 and integrated by the external chargeamplifier circuits 286. The row may then be switched back to anon-conducting state, and the process is repeated for each row until theentire array of photosensor cells 212 has been read out. The integratedsignal outputs are transferred from the external charge amplifiers 286to an analog-to-digital converter (ADC) 288 using a parallel-to-serialconverter, such as multiplexer 287, which together comprise read-outcircuit 230.

This digital image information may be subsequently processed by imageprocessing system 34 to yield a digital image which may then bedigitally stored and immediately displayed on monitor 26, or it may bedisplayed at a later time by accessing the digital electronic memorycontaining the stored image. The flat panel DR detector 40 having animaging array as described with reference to FIG. 2 is capable of bothsingle-shot (e.g., static, radiographic) and continuous (e.g.,fluoroscopic) image acquisition.

FIG. 3 shows a perspective view of an exemplary prior art generallyrectangular, planar, portable wireless DR detector 300 according to anembodiment of DR detector 40 disclosed herein. The DR detector 300 mayinclude a housing portion 314 that surrounds a multilayer structurecomprising the photosensor array portion 22 of the DR detector 300. Thehousing portion 314 of the DR detector 300 may include a continuous,rigid, x-ray opaque material or, as used synonymously herein aradio-opaque material, surrounding an interior volume of the DR detector300. The housing portion 314 comprises four edges 318, extending betweenthe top side 321 and the bottom side 322, and arranged substantiallyorthogonally in relation to the top and bottom sides 321, 322. Thebottom side 322 may be continuous with the four edges and disposedopposite the top side 321 of the DR detector 300. The top side 321comprises a top cover 312 attached to the housing portion 314 which,together with the housing portion 314, substantially encloses themultilayer structure in the interior volume of the DR detector 300. Thetop cover 312 may be attached to the housing 314 to form a sealtherebetween, and be made of a material that passes x-rays 16 withoutsignificant attenuation thereof, i.e., an x-ray transmissive materialor, as used synonymously herein, a radiolucent material, such as carbonfiber and plastic, polymeric, or other plastic based material.

With reference to FIG. 4, there is illustrated in schematic form anexemplary cross-section view along section A-A of the exemplaryembodiment of the DR detector 300 (FIG. 3). For spatial referencepurposes, one major surface of the DR detector 400 may be referred to asthe top side 451 and a second major surface may be referred to as thebottom side 452, as used herein. The embodiment of the DR detector 400depicted in FIG. 4 may be referred to herein as a “standard” DRdetector. The multilayer structure is disposed within the interiorvolume 450 enclosed by the housing 314 and top cover 312 and may includea substantially planar scintillator layer 404 over the two-dimensionalimaging sensor array 12 shown schematically as the device layer 402. Thescintillator layer 404 may be directly under (e.g., directly connectedto) the substantially planar top cover 312, and the imaging array 402may be directly under the scintillator 404. Alternatively, a flexiblelayer 406 may be positioned between the scintillator layer 404 and thetop cover 312 as part of the multilayer structure to provide shockabsorption. The flexible layer 406 may be selected to provide an amountof flexible support for both the top cover 312 and the scintillator 404,and may comprise a foam rubber type of material. The layers justdescribed comprising the multilayer structure each may generally beformed in a rectangular shape and defined by edges arranged orthogonallyand disposed in parallel with an interior side of the edges 318 of thehousing 314, as described in reference to FIG. 3.

A substrate layer 420 may be disposed under the imaging array 402, suchas a rigid glass layer upon which the array of photosensors 402 isformed, and may comprise another layer of the multilayer structure.Under the substrate layer 420 a radio-opaque shield layer 418 may beused as an x-ray blocking layer to help prevent scattering of x-rayspassing through the substrate layer 420 as well as to block x-raysreflected from other surfaces in the interior volume 450. Readoutelectronics, including the scanning circuit 28, the read-out circuit 30,and the bias circuit 32 (all of FIG. 1) may be formed co-planar with theimaging array 402 or, as shown, may be disposed below frame supportmember 416 in the form of integrated circuits electrically connected toprinted circuit boards 424. The frame support member 416 is fixed to thehousing 314 using frame support beams 422 to provide support for themultilayer structure just described. The imaging array 402 iselectrically connected to the integrated circuit readout electronics 424over a flexible connector 428 which may comprise a plurality offlexible, sealed conductors. X-ray flux may pass through the radiolucenttop panel cover 312, in the direction represented by an exemplary x-raybeam 16, and impinge upon scintillator 404 where stimulation by thehigh-energy x-rays 16, or photons, causes the scintillator 404 to emitlower energy photons as visible light rays which are then received inthe photosensors of imaging array 402. The frame support member 416 maysecurely mount the multilayer structure to the housing 314 and mayfurther operate as a shock absorber by disposing elastic pads (notshown) between the frame support beams 422 and the housing 314.Fasteners 410, such as screws, may be used to fixedly attach the topcover 312 to the housing 314 and create a seal therebetween in theregion 430 where they come into contact. In one embodiment, an externalbumper 412 may be attached along the edges 318 of the DR detector 400 toprovide additional shock-absorption.

FIG. 5 illustrates operation of an embodiment of an imaging system 500which may be used for long-length radiographic imaging of a stationarysubject (not shown) positioned between an x-ray source 501 and DRdetector 400. The x-ray radiation source 501 in the first position 502is aimed at DR detector 400 in position 504 to capture a firstradiographic image of the subject. In the embodiment shown in FIG. 5,the x-ray radiation source may be tilted in the direction indicated byarrow 508 to a second position 512 and aimed at DR detector 400 inposition 506 to capture a second image of the stationary subject,wherein the first and second images each include an image of a differentregion of the same subject. In the embodiment of FIG. 5, a single DRdetector 400 may be moved in the direction indicated by arrow 505 fromthe first position 504 to the second position 506 to capture the twoimages of the subject as just described. In another embodiment, twoseparate DR detectors 400 may be used, one in each of positions 504 and506, wherein each DR detector 400 is exposed to one radiographic pulsefrom the x-ray source 501 firing first and second radiographic energypulses at positions 502 and 512. In another embodiment, the DR detector400 may be moved to one or more intermediate positions between positions504 and 506, with corresponding intermediate tilt positions of the x-raysource 501 between positions 502 and 512 to capture one or moreadditional radiographic images. In another embodiment, the x-ray sourcemay be attached to a support at a fixed angle such that the x-ray source501 is not tiltable, rather, the support is configured to movevertically and is used to translate the x-ray source 501 to a positioncorresponding to the DR detector positions 504 and 506, or to theintermediate positions of the DR detector 400 as just described. Thus,it should be understood that embodiments of imaging system 500 mayinclude various combinations of one or more DR detectors 400, which maybe fixed or moveable, together with an x-ray source 501 that may betiltable and/or vertically translatable. In one embodiment, the one ormore positions of DR detector 400 may overlap, resulting in a pluralityof captured radiographic images that may be stitched together into onelong-length digital image of the subject using knowncomputer-implemented image reconstruction processing techniques.

FIG. 6 illustrates in schematic form another exemplary cross-sectionview along section A-A of the exemplary embodiment of the DR detector300 (FIG. 3). Several of the components in the DR detector 600illustrated in FIG. 6 are similar in most respects to the components asdescribed with respect to the DR detector 400 of FIG. 4 and areidentified with the same element numerals. The description of thosecomponents bearing the same element numerals is not repeated here. TheDR detector 600 comprises a housing 614 having a portion made from aradio-opaque material extending along a bottom portion of the DRdetector 600 and also continuously forms at least one edge of thehousing 614 which, in the perspective of FIG. 6, is located to the leftof the interior volume 450. In separate embodiments, the radio-opaqueportion of the housing 614 may continuously extend long one, two, orthree edges of a DR detector 600 having four edges. If the radio-opaqueportion of the housing 614 extends along two edges, it may extend alongany two adjacent and substantially perpendicular edges or along any pairof opposite substantially parallel edges of the DR detector 600.

In the exemplary embodiment of FIG. 6, a portion of the housing 612 isformed from a radiolucent material. This portion of the housing maycomprise a continuous extension of the top cover 312 (FIG. 4) to form aportion of the housing 612 for the DR detector 600 that is transparentto x-ray radiation. In separate embodiments, the radiolucent portion ofthe housing 612 may continuously extend along one, two, or three edgesof a DR detector 600 having four edges. If the radiolucent portion ofthe housing 612 extends along two edges, it may extend along any twoadjacent substantially perpendicular edges or along any pair of oppositesubstantially parallel edges of the DR detector 600. In order to fastenthe radiolucent portion of the housing 612, a fastener 611, similar inmaterial and shape as fastener 410, may be used in the bottom side ofthe DR detector to sealingly fasten the radiolucent edge of the housing612 to the frame support 416 or to a frame support beam 422. At theedges of the DR detector 600 where the radio-opaque housing 614 extendsalong the edges toward the top side 451, the fastener 410 may used asdescribed herein to sealingly fasten it to the radiolucent portion ofthe housing 612. The fastener 611 is positioned in the bottom side 452to minimize or eliminate placement of any DR detector components thatare not radiolucent above, or beyond an edge of, the imaging layer 402closest to a radiolucent edge of the DR detector 600. This helps toprevent artifacts appearing on radiographic images captured usingmultiple overlapping DR detectors 600 as described hereinbelow.Similarly, the integrated circuit readout electronics 424 are positionedproximate a (bottom) side of the sensor array imaging device layer 402that is opposite the x-ray source to minimize or eliminate placement ofany electronic components that are not radiolucent above, or beyond anedge of, the imaging device layer 402 closest to a radiolucent edge ofthe DR detector 600.

FIG. 7 illustrates in schematic form another exemplary cross-sectionview along section A-A of the exemplary embodiment of the DR detector300 (FIG. 3). Several of the components in the DR detector 700illustrated in FIG. 7, such as the multilayer structure, are similar inmost respects to the components as described with respect to the DRdetector 400 of FIG. 4 and are identified with the same elementnumerals. The description of those components bearing the same elementnumerals is not repeated here. The DR detector 700 comprises a housinghaving a portion made from a radio-opaque material 714 extending along abottom portion of the DR detector 700 and may continuously form one ortwo edges of the housing 714 wherein, in the perspective of FIG. 7, onesuch edge may be located behind the multilayer structure as depictedtherein. In separate embodiments, the radio-opaque portion of thehousing 714 may continuously extend long one or two edges of the housing712 of the DR detector 700 having four edges. If the radio-opaqueportion of the housing 714 extends along two edges, it may extend alongopposite edges of the DR detector 700.

In the exemplary embodiment of FIG. 7, a portion of the housing 712 isformed from a radiolucent material. This portion of the housing maycomprise a continuous extension of the top cover 312 (FIG. 4) to formopposite edges of the housing 712 for the DR detector 700 that aretransparent to x-ray radiation. In separate embodiments, the radiolucentportion of the housing 712 may continuously extend along two, three, orall edges of a DR detector 700 having four edges. In the perspective ofFIG. 7, two opposite edges (left and right) are formed from aradiolucent material, such as a carbon fiber reinforced plastic,polymeric, or other plastic based material. The housing 712 may extendvertically between the top side and the bottom side, or it may extend ata non-orthogonal angle therebetween, as shown in FIG. 7. In order tofasten the radiolucent portion of the housing 712, fasteners 711,similar in material and shape as fastener 410, may be used in the bottomside of the DR detector to sealingly fasten the radiolucent edge of thehousing 712 to the frame support 416, or to the frame support beam 422,as shown. The fasteners 711, as well as integrated circuit readoutelectronics 424 are positioned proximate the bottom side 452, which is aside of the sensor array imaging device layer 402 that is opposite thex-ray source to minimize or eliminate placement of any DR detectorcomponents that are not radiolucent above, or beyond an edge of, theimaging layer 402 closest to a radiolucent edge of the DR detector 600.This helps to prevent artifacts appearing on radiographic imagescaptured using multiple overlapping DR detectors 700 as describedhereinbelow.

As described herein, DR detector embodiments 400, 600, and 700 areusable individually, as in standard diagnostic radiographic imagingpractice, and may be combined, or tiled, as described herein, forlong-length imaging. FIG. 8 illustrates a side view of an exemplaryarrangement of three DR detectors including two standard DR detectors400, and a central DR detector 700, as describe herein with reference toFIG. 7, having at least two opposite edges of its housing formed fromradiolucent material that each overlap one edge of one of the standardDR detectors 400, as shown. The central DR detector 700 is positionedforward of the standard DR detectors 400 in relation to an x-ray energysource positioned to emit x-rays in a direction as depicted in FIG. 4and FIG. 7. The central DR detector includes an imaging array layerhaving one of its edges 705 overlapping an edge of the imaging arraylayer 307, in a corresponding first one of the standard DR detectors400, by a distance 820, and an opposite edge of the imaging array layer707 overlapping an edge of the imaging array 305, in a correspondingsecond one of the standard DR detectors 400, by a distance 821. Theoverlapping distances 820, 821 may be equivalent or different. Theoverlap distance is not critical to the presently disclosed invention,and may range from one or more millimeters to tens or hundreds ofmillimeters. Because the edges of the DR detector 700 that overlap theedges of the standard DR detectors 400 are radiolucent, and haveeliminated or minimized components, such as electronic readout circuits,beyond the edges of the imaging layer 402 therein, a radiographic imagecaptured simultaneously by the three detectors as depicted in FIG. 8,will not include unnecessary artifacts in the portions of theradiographic image captured by the standard DR detectors 400 caused byradio-opaque components in the central DR detector 700 that otherwisewould be disposed therein beyond the overlapping region if DR detector700 was configured as a standard DR detector. One advantage of theembodiment depicted in FIG. 8 is that the two prior art standarddetectors 400 may be used to capture a long-length image when combinedas shown with only one new modified DR detector 700. The embodimentillustrated in FIG. 8 does not require obtaining several DR detectorswith modified radiolucent edges. Thus, a radiographic imagesimultaneously captured by the three DR detectors arranged as in FIG. 8,may be accurately stitched together, without having to mask or processunnecessary artifacts, using standard computer implemented digitalreconstruction techniques. Such known digital reconstruction methodsinclude techniques for correcting geometric alignment of images from DRdetectors having different source-to-image distance. In the exampleembodiment shown in FIG. 8, a source-to-image distance of the DRdetector 700 may be less than that of the DR detectors 400.

FIG. 9 illustrates a side view of an exemplary arrangement of DRdetectors including one standard central DR detector 400, and two DRdetectors 600, as described herein with reference to FIG. 6, each havingone edge of its housing formed from radiolucent material that overlapsone edge of the standard central DR detector 400, as shown. The centralstandard DR detector 400 is positioned rearward of the DR detectors 600in relation to an x-ray energy source positioned to emit x-rays in adirection as depicted in FIG. 4 and FIG. 6. The central standard DRdetector 400 includes an imaging array layer having one of its edges 313overlapped by an edge of the imaging array layer 607 in a correspondingfirst one of the DR detectors 600 by a distance 822, and an oppositeedge of the imaging array layer 311 overlapped by an edge of the imagingarray layer 605 by a distance 823 in a corresponding second one of theDR detectors 600. The overlapping distances 822, 823 may be equivalentor different. The overlap distance is not critical to the presentlydisclosed invention, and may range from one or more millimeters to tensor hundreds of millimeters. Because the respective edge of each of theDR detectors 600 that overlaps the edge of the standard DR detector 400is radiolucent, and has eliminated or minimized radio-opaque components,such as integrated electronic read out circuits, beyond the edge of theimaging layer therein, a radiographic image captured simultaneously bythe three detectors as depicted in FIG. 9, will not include unnecessaryartifacts in the portion of the radiographic image as captured by thestandard DR detector 400 caused by radio-opaque components in the DRdetectors 600 that otherwise would be disposed therein beyond theoverlapping region if DR detectors 600 were configured as standard DRdetectors. One advantage of the embodiment depicted in FIG. 9 is that aprior art standard detector 400 may be used to capture a long-lengthimage when combined as shown with two new modified DR detectors 600 eachhaving only one edge modified to be radiolucent. The embodimentillustrated in FIG. 8 does not require obtaining several DR detectorswith modified radiolucent edges. Thus, a radiographic imagesimultaneously captured by the three DR detectors arranged as in FIG. 9,may be accurately stitched together without having to mask or processunnecessary artifacts using standard computer implemented digitalreconstruction techniques. Such known digital reconstruction methodsinclude techniques for correcting geometric alignment of images from DRdetectors having different source-to-image distance. In the exampleembodiment shown in FIG. 9, a source-to-image distance of the DRdetectors 600 may be less than that of the DR detector 400.

FIGS. 10 and 11 illustrate top views of the DR detector arrangements asdepicted in FIGS. 8 and 9, respectively. As shown, two standard DRdetectors 400 are positioned rearward of the DR detector 700 in FIG. 10,in relation to an x-ray source that, in the perspective of FIG. 10,emits x-ray energy into the page. The DR detector 700 includesradiolucent edges at its top and bottom edges in the Figure, whichoverlap the edges of the DR detectors 400, as described in relation toFIG. 8. In FIG. 11, two DR detectors 600, each as described andconfigured in the description of FIG. 6, are positioned forward of thestandard DR detectors 400 in FIG. 11, in relation to an x-ray sourcethat, in the perspective of FIG. 11, emits x-ray energy into the page.The DR detectors 600 each include at least one radiolucent edge (top orbottom edge) which overlaps a corresponding edge of the standard DRdetector 400, as described in relation to FIG. 9. While particulararrangements of DR detectors have been illustrated in FIGS. 8-11, itshould be noted that those skilled in the art may envisage that variouscombinations of DR detectors may be implemented in various geometriccombinations. Thus, different types of DR detectors may be utilized inupper, central, or lower positions, or may be used in combination withfour or more detectors, having edges overlapping, wherein each of the DRdetectors may be configured to include one, two, three, or fourradiolucent edges. Such combinations are considered to be within thescope of the present invention so long as any radio-opaque edges of a DRdetector do not interfere with the x-ray beams incident upon an imagingarray of another DR detector. Such radio-opaque edges may be positionedrearward of another overlapping DR detector, or may be positioned on anexterior border of the arrangement of DR detectors. Alternatively, someor all of the tiled DR detectors may be arranged in a staggered stepwisefashion (FIG. 13), rather than having one central DR detector positionedforward or rearward of the other detectors.

FIG. 12A illustrates a DR imaging system 1200 using the arrangement ofDR detectors as described in relation to FIG. 9 and FIG. 11 for use in along-length imaging exposure. DR detector 1201 may comprise a wired orwireless DR detector of the type 600 described in relation to FIG. 6; DRdetector 1202 may comprise a wired or wireless standard DR detector typeof the type 400 described in relation to FIG. 4; and DR detector 1203may comprise another wired or wireless DR detector of the type 600.X-ray source 501 may be fired once to expose a subject (not shown) to anx-ray beam 16 when the subject is placed between the x-ray radiationsource 501 and the multiple DR detectors 1201-1203, to capture adistributed image of the subject that is simultaneously captured andstored by the multiple DR detectors 1201-1203. The captured images, eachcomprising a portion of the subject, one from each DR detector, may bestitched together using known computer implemented reconstructiontechniques to generate a single long-length composite image of thesubject. Part of the control operations carried out by the imageprocessing and control unit 34 may include wired or wirelesscommunication with the DR detectors 1201-1203 for verification that theDR detectors have been initiated and are all in a ready state beforeexposure, for synchronization, and for coordinating storage andidentification of image frame data from each of the detectors. Such amethod does not require time consuming repositioning of one or more DRdetectors 1201-1203, as well as not requiring repositioning of the x-raysource 501, or multiple exposures, as may be currently practiced toobtain a long-length radiographic image. The arrangement of DR detectors1201-1203 may be configured by attachment to a rigid structure 1200using a modified “bucky” arrangement to fix in position each of the DRdetectors 1201-1203, or the detectors 1201-1203 may be affixed to awall. Alternatively, the DR detector 1202 may be part of an existingpermanent radiographic imaging installation which is fixed in positionas shown, while the other two DR detectors 1201, 1203, may be portable(temporarily fixed) DR detectors. One embodiment of the presentinvention may comprise a retrofittable separate structure fortemporarily securing in position the DR detectors 1201 and 1203 as shownand allowing movement of the structure having these two detectors 1201,1203, to position them in front of (overlapping) the fixed installationof DR detector 1202, as will be described below in relation to FIG. 12B.Although the arrangement of DR detectors 1201-1203 has been illustratedas a vertical alignment wherein the imaging planes of the DR detectorsare vertical, it should be noted that any of the tiled arrangements ofDR detectors disclosed herein may be positioned in a substantiallyhorizontal alignment wherein the imaging planes of the DR detectors arehorizontal, such as may be used for a human patient who is lying down onan examination bed with an x-ray source positioned above the patient, orthe DR detectors disclosed herein may be positioned in a substantiallyhorizontal alignment wherein the imaging planes of the DR detectors arevertical.

FIG. 12B illustrates a DR imaging system 1250 using an arrangement of DRdetectors as described in relation to FIG. 12A for use in a long-lengthimaging exposure, except that the DR detectors 1201, 1203, are affixedto a transport apparatus 1251 comprising a support post 1254 attached toa base 1256 outfitted with means for transporting the apparatus 1251 andDR detectors 1201, 1203, such as wheels 1257 which may include freelyrotatable wheels, lockable wheels, wheels that may be lowered or raisedby hand cranking or by electric motor under operator control, wheelsthat are not motor-assisted, and motor driven wheels that may be poweredby an electric motor to assist in manually transporting the apparatus1251. The support post 1254 secures in vertical relative position the DRdetectors 1201, 1203 with a preselected gap size therebetween 1255sufficient for the respective bottom and top edges of the DR detectors1201, 1203, to overlap a top and bottom edge of DR detector 1202, aspreviously described. As mentioned above, the DR detector 1202 mayrepresent a standard prior art DR detector permanently installed on onewall 1252 such as in a medical facility imaging room. The DR detector1202 may be used alone with x-ray source 501 for standard non-elongatedradiographic imaging and, in the case where a long-length radiographicimage may be desired, the apparatus 1251 may be rolled into position1260 along a floor of an imaging room. Similarly, DR detectors 1201,1203, may be usable individually for performing standard radiographicimaging of patients and may be inserted or attached to support post 1254to configure the transport apparatus 1251 as described herein. Thus, thetransportable pair of DR detectors 1201, 1203, may be advantageouslyaffixed to the transport apparatus 1251 to provide a capability toeasily convert the permanent installation of the standard DR detector1202 into the long-length imaging system 1250 when combined as shownwith two new modified DR detectors of the type 600 each having one ormore edges being radiolucent.

As before, x-ray source 501 may be fired once to expose a subject (notshown) when the subject is placed in front of the multiple DR detectors1201-1203. Part of the control operations carried out by the imageprocessing and control unit 34 may include wired or wirelesscommunications, wherein wireless communications are represented aswireless transmission signals 1258, with the DR detectors 1201-1203,such as waiting for and synchronizing ready state signals from allactivated DR detectors 1201-1203 before an exposure by x-ray source 501.Such a method does not require time consuming repositioning of one ormore DR detectors 1201-1203, as well as not requiring repositioning ofthe x-ray source 501, or multiple exposures, as may be currentlypracticed to obtain a long-length radiographic image.

FIG. 13 illustrates an embodiment of a DR imaging system 1300 whereinmore than three DR detectors are positioned in an overlapping fashion tocapture a long-length radiographic image. X-ray source 501 may emit asingle radiographic energy pulse that is received and captured by DRdetectors 1301-1305 as shown. A subject positioned in front of the DRdetectors 1301-1305 may result in radiographic images being generated inthe DR detectors 1301-1305, each comprising a portion of a radiographicimage of the subject using the single radiographic energy pulse. Asshown, DR detector 1301, the uppermost DR detector as shown, isillustrated as a DR detector 600 as described herein with reference toFIG. 6. Because DR detector 1301 is not positioned forward of another DRdetector, it may alternatively comprise a standard DR detector such asthe DR detector 400 described in relation to FIG. 4. Moreover, DRdetector 1301 may comprise a DR detector such as the DR detector 700described in relation to FIG. 7. Such alternate configurations areconsidered to be encompassed by the present disclosure because theyembody preferred configurations wherein a radio-opaque edge of any DRdetector used does not overlap the imaging array of another DR detectorpositioned behind it. In similar fashion, DR detector 1302, second fromthe top as shown, may comprise a detector of the type described inrelation to FIG. 7 wherein opposite edges (top and bottom edges in theperspective of FIG. 13) are configured to be radiolucent; DR detector1303, third from the top as shown, may comprise a standard DR detector400 of the type described in relation to FIG. 4, or it may comprises aDR detector 600 or 700 as described in relation to FIG. 6 and FIG. 7,respectively; DR detector 1304, fourth from the top as shown, maycomprise a DR detector 600 as described in relation to FIG. 6 whereinonly its upper edge is configured to be radiolucent; and DR detector1305, at the bottom of the arrangement as shown, may similarly comprisea DR detector 600 as described in relation to FIG. 6 wherein only itsupper edge is configured to be radiolucent. The detectors 1303-1305 arepositioned in a staggered stepwise arrangement, which stepwisearrangement may comprise an alternative arrangement for all the DRdetectors 1301-1305, as desired. As shown, the DR detectors 1301-1305may be fixed to a support structure 1300 for securing in position the DRdetectors 1301-1305.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, an apparatus, and a method, forcapturing long length images of a subject using multiple DR detectors.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

What is claimed is:
 1. A digital radiographic detector comprising: ahousing comprising a top side, a bottom side substantially parallel tothe top side, and a plurality of edges extending between a periphery ofthe top side and a periphery of the bottom side to form an interiorvolume of the housing; and a multilayer imaging structure within theinterior volume of the housing, the multilayer imaging structurecomprising a substantially planar imaging side configured to face thetop side of the housing and to face an external radiographic energysource emitting radiographic energy toward the top side of the housing,wherein the top side of the housing comprises a radiolucent material, atleast one of the plurality of edges of the housing is made from aradiolucent material, and wherein at least one of the plurality of edgesof the housing is made from a radiopaque material.
 2. The detector ofclaim 1, wherein the multilayer imaging structure further comprises: animaging device layer to receive light energy; and a scintillator layeradjacent the device layer, the scintillator layer to convert theradiographic energy to the light energy.
 3. The detector of claim 2,wherein the top side of the housing is sealingly attached to the atleast one of the plurality of edges of the housing made from theradiopaque material.
 4. The detector of claim 3, wherein the bottom sideof the housing comprises a radiopaque material, the bottom side of thehousing is sealingly attached to the at least one of the plurality ofedges of the housing made from the radiolucent material.
 5. The detectorof claim 2, further comprising a scanning circuit, a read-out circuit,and a bias circuit all enclosed within the interior volume of thehousing and in electrical communication with the imaging device layer.6. The detector of claim 2, further comprising a transmitter forwirelessly communicating with an image control processing system and forwirelessly transmitting a ready signal to the image control processingsystem.
 7. A digital radiography system comprising: an x-ray sourceconfigured to emit x-rays; a first DR detector comprising: a housingcomprising a top side, a bottom side substantially parallel to the topside, and a plurality of edges extending between a periphery of the topside and a periphery of the bottom side to form an interior volume ofthe housing; and a multilayer structure within the interior volume ofthe housing, the multilayer structure comprising a substantially planarimaging side configured to face the top side of the housing and to facethe x-ray source emitting the x-rays toward the top side of the housing,an imaging device layer to receive light energy, and comprising ascintillator layer adjacent the device layer, the scintillator layer toconvert the x-rays to the light energy, wherein the top side of thehousing comprises a radiolucent material, and wherein two opposingparallel edges of the plurality of edges of the housing are made from aradiolucent material; and second and third DR detectors each positionedbehind one of the two opposing parallel edges of the first DR detectorwith respect to the x-ray source and each comprising a radiopaquehousing without radiolucent edges.
 8. The system of claim 7, wherein thetop side of the housing comprises an outermost top surface of the firstDR detector.
 9. The system of claim 8, wherein the top side of thehousing extends continuously to form the two opposing parallel edges ofthe plurality of edges of the housing made from the radiolucentmaterial.
 10. The system of claim 7, further comprising an imageacquisition control system configured to wirelessly communicate with thefirst, second, and third DR detectors and to wirelessly receive a readysignal from each of the first, second, and third DR detectors beforeactivating the x-ray source.
 11. A long-length imaging systemcomprising: first and second DR detectors, each comprising: a housingcomprising a top side, a bottom side substantially parallel to the topside, and a plurality of edges extending between a periphery of the topside and a periphery of the bottom side to form an interior volume ofthe housing; and a multilayer structure within the interior volume ofthe housing, the multilayer structure comprising a substantially planarimaging side configured to face the top side of the housing, an imagingdevice layer to receive light energy, and comprising a scintillatorlayer adjacent the device layer, the scintillator layer to convertradiographic energy to the light energy, wherein the top side of thehousing comprises a radiolucent material, and wherein only one edge ofthe plurality of edges of the housing is made from a radiolucentmaterial; and a third DR detector disposed behind the first and secondDR detectors, such that said only one radiolucent edge of the first andsecond DR detectors each overlaps a different parallel edge of the thirdDR detector, the overlapped edges of the third DR detector comprisingradiopaque edges.
 12. The system of claim 11, further comprising atransportable support structure securing in a vertical relative positionthe first and second DR detectors with a preselected gap sizetherebetween.
 13. The system of claim 12, wherein the transportablesupport structure comprises means for moving the transportable supportstructure such that the first and second DR detectors are simultaneouslypositioned forward of the third DR detector.
 14. The system of claim 13,wherein the means for moving the transportable support structurecomprises wheels powered by an electric motor.
 15. The system accordingto claim 11, further comprising an x-ray source, and wherein the systemis configured to capture a portion of a radiographic image of a subjecton each of the first, second, and third DR detectors simultaneouslyusing one exposure by the x-ray source.
 16. The system of claim 15,wherein the preselected gap size is large enough for the third DRdetector to be exposed by the one x-ray exposure.
 17. The system ofclaim 15, further comprising an image acquisition control systemconfigured to wirelessly communicate with each of the first, second, andthird DR detectors and to wirelessly receive a ready signal from each ofthe first, second, and third DR detectors before activating the x-raysource.
 18. The system of claim 15, wherein the third DR detector is anon-portable DR detector fixed in a stationary position, and wherein thefirst and second DR detectors are each a portable independently usableDR detector.
 19. The system of claim 11, wherein the first, second andthird detectors are disposed along a horizontal axis.